10, 000

10, 000

MIT June 2010 1OEIT Star BioChem (LA and KMV)

10, 000 DNA lesionsX 1 trillion cells

10,000,000,000,000,000

MIT June 2010 2OEIT Star BioChem (LA and KMV)

DNA damage leads to mutations

MIT June 2010 3OEIT Star BioChem (LA and KMV)

DNA damage leads to mutations

5) UV rays(sun)

4) oxidation(respiration, smoking)

1) toxic chemicals(industrial & environmental)

2) X-rays(clinic)

3) viruses(HPV)

MIT June 2010 4OEIT Star BioChem (LA and KMV)

DNA damage leads to mutations

UV rays(sun)

oxidation(respiration, radiation, smoking)

toxic chemicals(industrial & environmental)

X-rays(clinic)

viruses(HPV)

mutations disease

MIT June 2010 5OEIT Star BioChem (LA and KMV)

Oxidation can cause mutations in DNA

MIT June 2010 6OEIT Star BioChem (LA and KMV)

Oxidation can cause mutations in DNA

MIT June 2010 7OEIT Star BioChem (LA and KMV)

Oxidation can cause mutations in DNA

MIT June 2010 8OEIT Star BioChem (LA and KMV)

DNA glycosylase proteins help repair DNA damage caused by oxidation

DNA glycosylases

MIT June 2010 9OEIT Star BioChem (LA and KMV)

Today’s activity: explore DNA glycosylases with Star BioChem (You can find it online too!)

humanhOGG1(37 °C)

archeabacteriaPa-AGOG(100 °C!)

MIT June 2010 10OEIT Star BioChem (LA and KMV)

Proteins perform many important biological functions

hemoglobincarry oxygen in the blood

F1 ATPasegenerate energy

antibodyprotect against

infections

aquaporinwater transport

microtubulescell division

Protein Data Bank websiteMIT June 2010 11OEIT Star BioChem (LA and KMV)

The function of a protein is determined by its structure

structure function

MIT June 2010 12OEIT Star BioChem (LA and KMV)

These two proteins both fix the same DNA defect.

humanhOGG1

archeabacteriaPa-AGOG

Protein Evolution: 1) Proteins with similar functions tend to have similar 3D structures.

2) Proteins with similar 3D structures DO NOT ALWAYS have exactly the same amino acid sequence. The folding is important for function.

MIT June 2010 13OEIT Star BioChem (LA and KMV)

Amino Acids Identify the amino group, the acid group, and

the side chains. The side chains are also called “R groups” (R = residues)

Acid RED Base BLUE

Hydrophobic YELLOW

(Polar) Hydrophilic GREEN

MIT June 2010 14OEIT Star BioChem (LA and KMV)